4.1.10. Delt: delta line model

The delta line model is a simple model for an infinitely narrow emission line.

The spectrum is given by:

F(E) = A \delta(E-E_0),

where E is the photon energy in keV, F the photon flux in units of 10^{44} \ \mathrm{ph} \ \mathrm{s}^{-1} \ \mathrm{keV}^{-1}, E_0 is the line energy of the spectral line (in keV) and A is the line normalisation (in units of 10^{44} \ \mathrm{ph} \ \mathrm{s}^{-1}). The total line flux is simply given by A.

To ease the use for dispersive spectrometers (gratings) there is an option to define the wavelength instead of the energy as the basic parameter. The parameter type determines which case applies: type=0 (default) corresponding to energy, type=1 corresponding to wavelength units.


When changing from energy to wavelength units, take care about the frozen/thawn status of the line centroid and FWHM.


You need to do a “calc” or “fit” command to get an update of the wavelength (for type=0) or energy (type=1).

The parameters of the model are:

norm : Normalisation A, in units of 10^{44} \ \mathrm{ph} \ \mathrm{s}^{-1}. Default value: 1.
e : The line energy E_0 in keV. Default value: 6.4 keV.
type : The type: 0 for energy units, 1 for wavelength units.
w : The line wavelength \lambda in Å. Default value: 20 Å.